1. Field of the Invention
This invention relates generally to semiconductor processing, and more particularly to stacked semiconductor chip devices with an polymeric filler and to methods of assembling the same.
2. Description of the Related Art
Stacked semiconductor chip devices present a host of challenges for package integration. Many of these technical challenges are associated with the differences in topography between the base chip and the one or more chips stacked thereon. One particular technical challenge associated with stacked chip devices is thermal management. Many conventional single chip semiconductor chip packages incorporate a heat spreader or lid that is placed in thermal contact with a backside of a semiconductor chip by way of a thermal interface material. Some conventional thermal interface materials consist of polymers such as thermal greases. For higher heat dissipation devices, package designers have turned to solder type thermal interface materials such as indium.
It is desirable, if indium is used as a thermal interface material, to ensure that the indium metallurgically bonds to both the base semiconductor chip and the overlying heat spreader in those designs where the stacked semiconductor chips have a smaller footprint than the base semiconductor chip. However, indium does not readily wet to many types of materials. Accordingly, a wetting film is typically formed on surfaces where metallurgical bonding with indium is desired.
In order for a conventional wetting film to successfully bond with indium, there should be no contaminants that might interfere with the bonding during a thermal reflow process. One potential contaminant that is an important feature of many semiconductor chip package designs is an underfill, which is placed between two substrates to lessen the effects of differences in the coefficients of thermal expansion between the two substrates. It is thus desirable to keep underfill from contaminating a portion of a wetting film slated for metallurgical bonding.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.